1. Field of the Invention
The present invention relates to an electrodeless lighting system using microwave and particularly, to a method for manufacturing a mesh screen of an electrodeless lighting system, capable of intercepting microwave and passing light generated in a bulb.
2. Description of the Background Art
An electrodeless lighting system is a device for emitting visible rays or ultraviolet rays by applying microwave to an electrodeless lamp, and therefore, has longer life span than that of incandescent lamp or fluorescent lamp which is generally used, and has higher lighting effect.
FIG. 1 is a longitudinal cross-sectional view showing a general electrodeless lighting system according to the conventional art.
The conventional electrodeless lighting system includes a magnetron 1 for generating microwave, a waveguide 3 for guiding the microwave generated from the magnetron 1, A bulb 5 for generating light as the material enclosed is plasma polymerized by the energy of the microwave transmitted through the waveguide 3 and a mesh screen 20, covered on the front side of the waveguide 3 and bulb 5, for intercepting leakage of microwave and passing the light emitted from the bulb 5.
The electrodeless lighting system additionally includes a high voltage generator 7 for transforming utility AC power to high voltage, a cooling apparatus 9 for cooling the magnetron 1, high voltage generator 7 and the like, a reflector 11 for intensively reflecting the light generated from the bulb 5 and a bulb motor 13 and bulb shaft 15, for cooling heat generated in discharging light by rotating the bulb 5.
In the electrodeless lighting system, when a driving signal is inputted to the high voltage generator 7, the high voltage generator 7 transforms a utility AC power to high voltage from the outside and supplies the high voltage into the magnetron 1.
The magnetron 1 generates a microwave having very high frequency oscillating by the high voltage supplied from the high voltage generator 7 and the microwave generated as above is eradiated into the mesh screen 20 through the waveguide 3, then, the material filled in the bulb 5 is discharged to generate light having a very peculiar discharge spectrum.
The light generated in the bulb 5 is reflected on the reflector 11 and the light is illuminated frontward as reflected by a mirror 12 and the reflector 9.
FIG. 2 is a perspective view showing a mesh screen used in the above electrodeless lighting system and FIG. 3 is a detail view showing xe2x80x9cAxe2x80x9d portion in FIG. 2.
With reference to FIG. 1, the mesh screen 20 formed in a metal mesh is assembled at the outlet portion 3a of the waveguide 3, intercepts the microwave transmitted through the waveguide 3 so that the microwave energy is transformed to be light in the bulb 5 and at the same time intercepts leakage of the microwave to the outside so that the light generated in the bulb 5 is penetrated to the outside.
With reference to FIGS. 2 and 3, such mesh screen includes a cylindrical part 21 where a plurality of holes 20b are formed except in a part at an opened part 20a by the etching processing and a cover part 25 formed in a convex shape, where a plurality of holes 20b are formed to be connected to the from portion of the cylindrical part 21 by the etching processing.
Here, the cylindrical part 21 includes a mesh portion 22 for intercepting microwave and passing light and a non-mesh portion 23 which is not etching processed to be fixed to the outlet part of the waveguide 3.
Such mesh screen 20 must be formed precisely, penetrate light emitted from the bulb 5 well and have heat resistance so that it can resist against heat generated from the bulb 5, since it intercepts leakage of the microwave forming a resonance region.
Here, the method for manufacturing such mesh screen 20 in accordance with the conventional art will be described with reference to FIG. 4.
Base metal is formed by cutting a metal thin film with a predetermined thickness made of stainless steel or phosphor bronze in the square shape or circular shape.
Holes having the mesh structure are formed by etching with solutions such as FeCl2 and the like to form a mesh structure on the base metal.
Here, it is desirable that the holes formed by etching on the metal thin film are formed with a size, capable of intercepting leakage of the microwave to the outside having the highest opening rate so that the light emitted from the bulb 5 in FIG. 1 is radiated to the outside as much as possible.
When the mesh structure is formed in the base metal, the cylindrical part 21 is manufactured by welding the metal to have a cylindrical shape as in FIG. 2 and then a mesh screen 20 with a side opened is formed by assembling by the method such as welding and the like.
Then, electric resistance of the surface is decreased as the light reflectivity of the surface of the mesh screen 20 becomes higher and the mesh screen is completed by plating as a three-step structure, performing the Ni plating process for plating Ni on the mesh screen 20 to improve heat resistance, Ag plating process for plating Ag and the Rh plating processing for plating Rh.
However, the mesh screen manufactured by the method for manufacturing the mesh screen in accordance with the conventional art, causes deformation of plated layers as residuals are evaporated at high temperature, if the mesh screen is exposed to the high temperature over 1000xc2x0 C. due to heat generated from the bulb 5, since various organic materials or acid radicals are remained when the plate of the mesh screen 20 is plated.
Also, separation between plated layers is occurred when the mesh screen 20 at high temperature is given thermal stress.
Therefore, in case the mesh screen is manufactured in the conventional manufacturing method, deformation or separation of the plated layer is occurred and discoloration or oxidation corrosion is accelerated when the mesh screen 20 is contacted with external air in the air cooling structure, thus to decrease security of the mesh screen 20 and shorten the life span.
Therefore, an object of the present invention is to provide a method for manufacturing a mesh screen of an electrodeless lighting system, capable of improving the security of the mesh screen and lengthening the life span of the mesh screen by performing vacuum heat-treating process in the plating process of the mesh screen to improve heat resistant characteristic and chemical resistant characteristic.
Another object of the present invention is to provide a method for manufacturing a mesh screen of an electrodeless lighting system, capable of improving optical character by endowing a self-clarifying function by plating the mesh screen and then coating photocatalytic substance.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a method for manufacturing a mesh screen of an electrodeless lighting system, including a mesh screen forming step for forming a mesh screen to have a mesh structure, a first plating step for plating first metal substance on the surface of the mesh screen, a vacuum heat-treating step for vacuum-heat-treating the mesh screen under the condition that the temperature is risen to a predetermined degree, a second plating step for plating second metal substance on the surface of the mesh screen and a photocatalytic coating step for coating photocatalytic substance on the surface of the mesh screen.
The first metal substance is Ni and the second metal substance is Ag.
The vacuum degree is 10xe2x88x927E Torr in the vacuum heat-treating step and the heat-treating is performed raising the heating temperature up to 700xc2x0 C.
Namely, the vacuum heat-treating step includes a temperature raising process for raising the temperature of the mesh screen from the room temperature to 650xc2x0 C., a holding process for vacuum-heat-treating the mesh screen at 650xc2x0 C. for a predetermined time, a coercive cooling process for coercively cooling the mesh screen and a natural cooling process for naturally cooling the mesh screen to room temperature.
The photocatalytic substance is an oxidized substance containing TiO2.
Also, the method for manufacturing the mesh screen of the electrodeless lighting system includes a first plating step for plating first metal substance on the surface of the mesh screen, a vacuum heat-treating step for vacuum-heat-treating the mesh screen under the condition that the temperature is risen up to 700xc2x0 C. and a second plating step for plating second metal substance on the surface of the mesh screen.
Also, the method for manufacturing the mesh screen of the electrodeless lighting system includes a mesh screen forming step for forming a mesh screen to have a mesh structure, a plating step for plating metal substance on the surface of the plated mesh screen and a photocatalytic coating step for coating photocatalytic substance on the surface of the mesh screen.
The foregoing and other, features, aspects and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.